1. Field of the Invention
This invention relates to a process for producing a dihydric phenol which comprises oxidizing a monohydric phenol by a peroxide compound in the presence of a ketone and a phosphoric acid.
2. Prior Art
As a process for producing a dihydric phenol by oxidizing a monohydric phenol by a peroxide compound in the presence of a catalyst, there has been known a process as mentioned below. For example, a process in which a reaction is conducted in the presence of a ketone and phosphoric acid using a catalyst such as sulfuric acid is disclosed in Japanese Provisional Patent Publications Nos. 65232/1977 and 65233/1977, etc. Sulfuric acid used in this process as a catalyst has a corrosive property, and therefore, a new catalyst substituting therefor has been desired to be developed. As a catalyst substituting sulfuric acid, for example, there have been descriptions on phosphotungstic acid and silicotungstic acid in Japanese Provisional Patent Publication No. 078843/1977, various kinds of sulfates in Japanese Provisional Patent Publication No. 130727/1975, and a clay mineral in Japanese Provisional Patent Publication No. 142026/1977, respectively. However, a yield of the product based on a peroxide compound is low, so that a development of a catalyst with a further higher activity has been expected.
An object of the present invention is to develop an acid catalyst with high activity and without a corrosive property in order to provide a process for producing a dihydric phenol with a high yield by oxidizing a monohydric phenol with a peroxide compound in the presence of a ketone and a phosphoric acid.
The present inventors have intensively studied to accomplish the above-mentioned object and as a result, they have found that a dihydric phenol can be obtained with a high yield by using a xcex2-zeolite which has no corrosive property when a dihydric phenol is produced by oxidizing a monohydric phenol with a peroxide compound in the presence of a ketone and a phosphoric acid.
That is, the present invention is a process for producing a dihydric phenol which comprises oxidizing a monohydric phenol by a peroxide compound in the presence of a xcex2-zeolite, a ketone and a phosphoric acid.
Also, the present invention is a process for producing a dihydric phenol which comprises oxidizing a monohydric phenol in the presence of a xcex2-zeolite, a ketone and a phosphoric acid, by feeding a monohydric phenol, hydrogen peroxide, a ketone and a phosphoric acid into a reactor in which a xcex2-zeolite is charged, to oxidize the monohydric phenol into a dihydric phenol, and delivering the resultant reaction mixture from the reactor.
In the following, the present invention will be explained in more detail.
As the monohydric phenol to be used in the present invention, there may be mentioned, for example, phenol, a monohydric monoalkyl phenol, a monohydric halogenated phenol and a monohydric polyalkyl phenol.
As the alkyl group contained in the monohydric monoalkyl phenol, there may be mentioned a straight or a branched alkyl group having 1 to 6 carbon atoms. A position of the alkyl group is not particularly limited as long as it does not participate in a reaction. As examples of these compounds, there may be mentioned o-, m- or p-cresol, o-, m- or p-ethylphenol, o-propylphenol, p-isopropylphenol, m-butylphenol, p-isobutylphenol, p-t-butylphenol, m-isobutylphenol, p-pentylphenol and p-hexylphenol.
As the halogen atom contained in the monohydric halogenated phenol, there may be mentioned a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. A number and a position of the halogen atoms are not particularly limited as long as they do not participate in a reaction. As examples of these compounds, there may be mentioned o-, m- or p-fluorophenol, o-, m- or p-chlorophenol, o-, m- or p-bromophenol, o-, m- or p-iodophenol, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-dichlorophenol, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-dibromophenol, 2,3,4-, 2,3,5-, 2,3,6-, 2,4,5-, 2,4,6- or 3,4,5-trichlorophenol.
As the alkyl group contained in the monohydric polyalkyl phenol, there may be mentioned a straight or a branched alkyl group having 1 to 6 carbon atoms. A number and a position of the alkyl groups are not particularly limited as long as they do not participate in a reaction. As examples of these compounds, there may be mentioned 2,3-, 2,4-, 2,5-, 2,6-, 3,5- or 3,4-dimethylphenol, 2,3,4-trimethylphenol, 2,3,5-, 2,3,6- or 3,4,5-trimethylphenol, 2,4,5-trimethylphenol, 2,3,4,5- or 2,3,5,6-tetramethylphenol, 2-ethyl-3-methylphenol, 3-t-butyl-4-methylphenol, 2-isopropyl-5-methylphenol, 2-pentyl-6-methylphenol and 3-hexyl-5-methylphenol.
As examples of the ketone to be used in the present invention, there may be mentioned a monoketone and a diketone. As the monoketone, a noncyclic or cyclic monoketone is mentioned. As the noncyclic monoketone, there may be mentioned, for example, a straight or branched aliphatic monoketone having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms and an aromatic monoketone. Hydrogen atom of these compounds may be substituted by a halogen atom (a fluorine atom, a chlorine atom, a bromine atom or an iodine atom). A number and a position of the halogen atoms are not particularly limited as long as they do not participate in a reaction.
As the straight aliphatic monoketone, there may be mentioned, for example, acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, 2-hexanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-octanone, 2-nonanone, 3-decanone, 6-undecanone, 2-tri-decanone, 7-tridecanone, 2-tetradecanone, 2-pentadecanone, 2-hexadecanone, 2-heptadecanone, 3-octadecanone, 4-nonadecanone, 1-chloro-2-propanone, 1-chloro-3-heptanone and 1-bromo-3-heptanone.
As the branched aliphatic monoketone, there may be mentioned, for example, 3-methyl-2-butanone, 3-methyl-2-pentanone, 4-methyl-2-pentanone, 3,3-dimethyl-2-butanone, 2,4-dimethyl-3-pentanone, 6-methyl-2-heptanone, 2,6-dimethyl-4-heptanone and 2,2,4,4-tetramethyl-3-heptanone. As the aromatic monoketone, there may be mentioned, for example, acetophenone, benzophenone, 1-phenyl-3-propanone, 1-phenyl-1-butanone, 1-phenyl-3-butanone, 1-phenyl-3-pentanone and 1,3-diphenyl-2-propanone.
As the cyclic monoketone, there may be mentioned, for example, a cycloalkyl monoketone having 5 to 12 carbon atoms. Hydrogen atoms of these compounds may be substituted by a halogen atom (a fluorine atom, a chlorine atom, a bromine atom and an iodine atom) or by a straight or a branched alkyl group having 1 to 6 carbon atoms. A number and a position of the substitute are not particularly limited as long as they do not participate in a reaction. As examples of these compounds, there may be mentioned cyclopentanone, cyclohexanone, cyclododecanone, 2-chlorocyclohexanone, 2-ethyl-1-cyclopentanone, 2-methyl-1-cyclohexanone.
As the diketone, there may be mentioned a noncyclic or cyclic diketone. As the noncyclic diketone, there may be mentioned, for example, a straight or a branched aliphatic diketone having 5 to 21 carbon atoms, preferably 5 to 12 carbon atoms and an aromatic diketone. Hydrogen atom of these compounds may be substituted by a halogen atom (a fluorine atom, a chlorine atom, a bromine atom or an iodine atom). A number and a position of the halogen atoms are not particularly limited as long as they do not participate in a reaction. As the straight aliphatic diketone, there maybe mentioned, for example, 2,3-butanedione, 2,4-pentanedione and 2,5-hexanedione. As the branched aliphatic diketone, there may be mentioned, for example, 2,5-dimethyl-3,4-hexanedione. As the aromatic diketone, there may be mentioned, for example, 1,2-diphenylethane-1,2-dione.
As the cyclic diketone, there may be mentioned, for example, a cyclic diketone having 5 to 12 carbon atoms. Hydrogen atom of these compounds may be substituted by a halogen atom (a fluorine atom, a chlorine atom, a bromine atom and an iodine atom) or by a straight or branched alkyl group having 1 to 6 carbon atoms. A number and a position of the substituent are not particularly limited as long as they do not participate in a reaction. As the cyclic diketone, there may be mentioned, for example, 1,4-cyclohexanedione.
Among the ketones to be used in the present invention, preferred are the straight or branched aliphatic monoketone or the cyclic monoketone, and more preferred are the straight or branched aliphatic monoketone, among which 4-methyl-2-pentanone and 3-pentanone are particularly preferred.
An amount of the ketone to be used is preferably 0.2:1 to 5:1 in terms of a molar ratio of the ketone to a peroxide compound (ketone:peroxide compound).
As the phosphoric acid to be used in the present invention, there may be mentioned, for example, orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, triphosphoric acid, tetraphosphoric acid, polyphosphoric acid, phosphoric anhydride and an aqueous phosphoric acid solution, among which the aqueous phosphoric acid solution is preferred. A concentration of the aqueous phosphoric acid solution is preferably 0.001 to 100% by weight.
An amount of the phosphoric acid to be used is preferably 0.0001:1 to 0.05:1 in terms of a weight ratio of the phosphoric acid to the monohydric phenol (phosphoric acid:monohydric phenol).
As the peroxide compound to be used in the present invention, there may be mentioned, inorganic peroxide compounds, for example, hydrogen peroxide, and organic peroxide compounds, for example, ketone peroxides and aliphatic percarboxylic acids.
As the ketone peroxides, there may be mentioned, for example, dialkyl ketone peroxides which have 3 to 20, preferably 3 to 10 carbon atoms, such as dimethyl ketone peroxide, diethyl ketone peroxide, methyl ethyl ketone peroxide, methyl-n-propyl ketone peroxide, methyl isopropyl ketone peroxide, and methyl isobutyl ketone peroxide.
As the aliphatic percarboxylic acids, there may be mentioned, for example, peracetic acid and perpropionic acid.
As hydrogen peroxide, 0.1% by weight or more of the aqueous hydrogen peroxide solution may be used, preferably 0.1 to 90% by weight, and more preferably 30 to 80% by weight.
Among the peroxide compounds to be used in the present invention, preferred are hydrogen peroxide and ketone peroxides. The ketone peroxides can be prepared by contacting ketone with hydrogen peroxide. The ketones to be used here are the same as mentioned before.
An amount of the peroxide compound to be used is preferably in the range of 1:1 to 1:100, more preferably in the range of 1:5 to 1:20 in terms of a molar ratio of the peroxide compound to the monohydric phenol.
In the present invention, a xcex2-zeolite is used as a catalyst. As the xcex2-zeolite, a proton type xcex2-zeolite is preferred, among which a proton type xcex2-zeolite carrying thereon at least one of an alkaline earth metal is especially preferred. A content of aluminum in the xcex2-zeolite is preferably in the range of 1:10 to 1:10000 in terms of an atomic ratio of aluminum to silicon (Al:Si).
An amount of the xcex2-zeolite to be used is preferably in the range of 1:1 to 1:500, more preferably in the range of 1:5 to 1:100 in terms of a weight ratio of the xcex2-zeolite to the monohydric phenol (xcex2-zeolite:monohydric phenol).
The xcex2-zeolite ma y be prepared according to a method described in Journal of Physical Chemistry, 104 (2000), pp. 2853 to 2859, or a commercially available product may be preferably used.
The proton type xcex2-zeolite is prepared according to a method described in the above-mentioned reference, etc. For example, it can be prepared by heating a xcex2-zeolite in an aqueous solution containing an ammonium ion such as an aqueous solution of ammonium nitrate, ammonium chloride, etc. (an ammonium salt concentration: 0.1 to 40% by weight) at 20 to 120xc2x0 C., for 1 to 20 hours, washing the resulting material by deionized water, etc., drying the same at 20 to 150xc2x0 C., and calcining the same at about 300 to 650xc2x0 C. for 1 to 10 hours.
The proton type xcex2-zeolite carrying thereon an alkaline earth metal may be obtained by introducing alkaline earth metals to the above-mentioned proton type xcex2-zeolite. As the alkaline earth metal, there may be mentioned beryllium, magnesium, calcium, strontium, and barium, among which magnesium, calcium, strontium and barium are preferable. As a method for introducing the metals, methods such as a conventionally used ion-exchange method, impregnation method, chemical vapor deposition (CVD) method, mechanical kneading method and the like are applicable, among which the ion-exchange method is preferable.
The proton type xcex2-zeolite carrying thereon an alkaline earth metal can be prepared by the ion-exchange method according to a method described in Monthly Journal of Institute of Industrial Science, 21, 7 (1969), pp. 453 to 454. For example, it can be prepared by heating a xcex2-zeolite in an aqueous solution containing alkaline earth metal ions such as an aqueous solution of a nitrate, a hydrochloride and a sulfate of an alkaline earth metal (a concentration of the alkaline earth metal salt: 0.1 to 40% by weight) at 20 to 120xc2x0 C., for 1 to 20 hours, washing the resulting material with deionized water, etc., drying the same at 20 to 150xc2x0 C. for 5 minutes to 24 hours, and calcining the same at about 300 to 650xc2x0 C. for 1 to 10 hours. An amount of the alkaline earth metal ion introduced into the proton type xcex2-zeolite is preferably in the range of 0.0001 to 10, more preferably 0.01 to 1, in terms of an atomic ratio of M2+/Al (M2+ represents an alkaline earth metal ion).
A shape of the xcex2-zeolite to be used may be mentioned powder, a granule, a pellet and the like.
As a shape of the xcex2-zeolite suitable for the preparation method of the dihydric phenol, for example, when a liquid phase batch system reactor is used for preparation, powder is preferably used, and when a liquid phase flow system reactor is used for preparation, a pellet and the like is preferably used.
In the preparation of the dihydric phenol, the reaction temperature is preferably 20 to 250xc2x0 C., more preferably 40 to 150xc2x0 C. The reaction time is not limited although it depends on a kind of the catalyst used and the reaction temperature employed. In addition, although the reaction can be conducted under an atmospheric pressure, it may be conducted under a reduced or increased pressure. The reaction can be conducted in a liquid phase, by a batch system, a flow system, a trickle bed system, etc.
In the process of the present invention, optionally, a complexing agent for metal ions, for example, monoalkyl phosphates and dialkyl phosphates, may be employed.
In the process of the present invention, the reaction is carried out, for example, by feeding a monohydric phenol, hydrogen peroxide, a ketone and a phosphoric acid into a reactor in which a xcex2-zeolite is charged, to oxidize the monohydric phenol into a dihydric phenol, and delivering the resultant reaction mixture from the reactor.
The dihydric phenol to be produced in the present invention is obtained as one kind or a mixture of several kinds corresponding to the structure of a monohydric phenol used as a starting material. In addition, these dihydric phenols can be obtained by separation and purification according to the conventional method.